GNSS (Global Navigation Satellite Systems) such as a GPS (Global Positioning System) are used for, for example, positioning by receiving GNSS signals broadcasted from positioning satellites. Each GNSS signal is comprised of a spread spectrum signal which is code modulated by a pseudo noise.
When receiving such a GNSS signal, if a signal other than the GNSS signal (hereinafter, referred to as the interference wave signal) is received, a disadvantage may be caused, for example, reception sensitivity to the GNSS signal degrades.
Therefore, Patent Document 1 and Patent Document 2 disclose interference wave signal removing devices for detecting and removing interference wave signals of which frequency bands are narrow (having narrow bands) different from GNSS signals. FIG. 1 is a block diagram of main circuits of the conventional interference wave signal removing device 100P disclosed in Patent Document 1.
The conventional interference wave signal removing device 100P disclosed in Patent Document 1 includes a controller 101P, a notch filter 102P, a frequency analyzer 103P, and a frequency scanner 104P. The controller 101P specifies a frequency of an interference wave signal based on a frequency spectrum of an input signal Si obtained from the frequency analyzer 103P and a frequency spectrum of an output signal Sop obtained from the frequency scanner 104P. Further specifically, the specification of the interference wave signal frequency is performed by the following processing. The controller 101P adjusts the attenuation property of the notch filter 102P to attenuate the interference wave signal component based on the information of the specified interference wave signal frequency.